Many people assume that once their solar panels have been installed, they will just be silently generating renewable energy and saving them money on their electricity bill. However, to find out how much you have actually saved each month, you need to monitor the generation properly and check the numbers regularly.
Start With Your Inverter App
All of the major systems such as SolarEdge, GivEnergy and Growatt have monitoring apps that allow you to view the amount of energy being generated by your solar panels in real time. Each day log onto the app to view the total amount of energy in kWh that has been generated for the month, not just the daily average. Write down the amount so you can refer back to it later. You’ll be surprised how quickly you’ll forget after three months whether March generated 180kWh or 280kWh of solar energy.
Check Your Smart Meter Figures Too
You can find out how your smart meter records your electricity use from your supplier’s website. Your in-home display or supplier’s app will show you the import and export of electricity in separate columns. By comparing these figures each month you can get an idea of how much of the electricity you have generated you are using and how much you are exporting to the grid and therefore not using.
Build A Simple Monthly Spreadsheet
Keep a basic spreadsheet to log your generation data, self-consumption, exports and your grid imports against your electricity bills for the relevant period. After six months you will have established trends and be able to see what’s going on with your electricity usage on your panel(s) over the seasons, e.g. why you seem to be importing more grid electricity in December compared to June for example.
Match Export Payments To Actual Units
Export payments are typically paid out on the amount of electricity you export in kWh. Some suppliers may pay out instantly, whilst others can take 1-3 months to settle. You can find the rate your supplier is paying out per kWh of export and the terms and conditions of how they pay out via the Smart Export Guarantee scheme website. You can also query with your supplier how they have calculated your payment. See also Solar Panel Installation Bristol. More detail on MCS-certified solar installers is set out in the published guidance.
Compare The Same Month Year On Year
Solar generation varies greatly with the seasons, so even though your bill may look lower in October compared to July for example, it does not necessarily mean that your solar savings are lower. Compare the same month from year to year (i.e. this October against last October) to get an accurate reading of your solar savings and whether your solar output and savings are improving, staying the same or decreasing.
Note Your Tariff Rate Each Time
It is also easy to mistake a fall in the amount of electricity you use for a fall in the amount of solar electricity you have generated. If the supplier has reduced their unit rate (the rate at which they charge you per unit of electricity you use) then your bill will go down but your solar savings will have gone down too. Just keep a note of the current rate and the standing charge too, and this will become very clear.
Watch For Unexplained Drops
As has already been mentioned, a drop in generation during a rainy month is normal, but a continued drop when things return to normal needs investigating. Bird mess and grime can have a serious impact on generation, as can a tree growing in your garden. In Bristol where I had my solar panel installation, we had an assessment of the exposure of my roof. This needs to be compared against the data for your installation to see if there are any changes in generation that could be caused by anything other than normal weather variations. A quick clean of your panels or an investigation as to why your inverter may be faulty could be all that is needed to solve the problem.
Review Quarterly, Not Daily
Tracking how your solar system is performing on an hourly basis is largely a waste of time. Your system is likely to be affected by many changes in the weather from one hour to the next. By tracking your system’s performance on a quarterly basis you will get a much better idea of how your system is performing. If you are thinking of doing any roof work or converting loft space into living space then it is worth looking at the Bristol City Council’s planning guidance on solar panels and how changes to your roof line could affect you in terms of shading your solar panels and therefore reducing your generation figures.
Continue to update your simple log throughout the year. Within a year you will have a useful reference on the season by season performance of your solar panels and how much they are saving you.